"I have matured a great deal in the past year and had to learn some hard lessons because of my actions," the star tells PEOPLE
Credit: Jason Merritt/Getty

High School Musical 3 star Justin Martin is speaking out after being sentenced to 18 months behind bars on Tuesday.

“I have matured a great deal in the past year and had to learn some hard lessons because of my actions,” Martin, 22, tells PEOPLE in an exclusive statement. “I should have acted more responsibly and taken my choices more seriously.”

The actor plead guilty to gun charges related a July 2015 arrest in Massachusetts. Martin says he has been making amends for that incident over the past year.

“This last year, I have been speaking at schools in Boston and educating high school students about making good choices, anti-gun violence and drug awareness,” Martin continues. “I focus on being accountable for your actions and emphasize that one mistake doesn’t have to define your life. I appreciate everyone’s support, especially my family and friends for standing by me and knowing that my choices that night are not reflective of my true character. I look forward to moving past this time in my life and getting back to my career. Thank you for all the positive messages and support.”

Martin will serve one year probation, but will be allowed to ask for the probation to be cut short if he complies with the terms of the probation by remaining drug and alcohol free and staying away from the area of the offense, a spokesperson for the Suffolk County, Massachusetts district attorney’s office says. Police say Martin pointed a gun at officers during the 2015 incident.

Martin’s attorney says the actor has “accepted responsibility for his mistakes.”

‎”The incident was a confrontation initiated by others who have a long history with law enforcement, and Justin reacted in a way that was inconsistent with his character,” says Martin’s attorney, Asha White. “At no time did Justin ever fire a gun at police officers. However, there was a circumstance when he pointed a gun at an officer who arrived in an unmarked car wearing plain clothes, mistakenly believing that they were part of the group of attackers. Justin’s attackers fired at police and also fired at Justin. Martin was offered a plea agreement that was the minimum possible sentence by the court, but it is a mandatory sentence in the state for possession of a firearm. Justin has no prior confrontations with law enforcement and is hopeful that he can move forward from this unfortunate incident.‎”

In addition to High School Musical 3, Martin’s credits include Denzel Washington‘s Flight and The Soloist with Jamie Foxx and Robert Downey Jr.